1. Field of the Invention
The present invention relates to methods of cooling computer systems, and more specifically to the operation of fans to flow air through computer systems.
2. Background of the Related Art
Computer systems come in various physical sizes, and in various configurations. These computer systems typically include fans, which circulate cool air through the system in order to keep the temperature of internal heat-generating components within thermal operating limits. Because small system fans are usually very inefficient from an electrical energy perspective, some chassis provide a common fan assembly that serves to cool multiple system boards.
Thermal limits are typically satisfied in a single motherboard/chassis arrangement by reading the internal CPU diodes and changing the speed of a dedicated fan assembly at prescribed temperature thresholds. However, this practice of reading CPU diodes can not be implemented easily in systems with shared infrastructure, such as systems with a shared fan assembly used to cool multiple system boards. In order to take advantage of the energy-efficient nature of a shared fans assembly in a chassis that supports multiple motherboards, a different thermal management scheme must be used.
One known thermal management scheme includes running the system fans at a constant elevated fan speed that will ensure adequate cooling of each of the multiple motherboards in the system chassis. This approach increases the amount of electrical energy consumed by operation of the fans, increases the thermal load on the datacenter from the excessive airflow through the fans, and increases the acoustic level caused by running the fans faster than is necessary to achieve optimal cooling.
Another thermal management scheme includes monitoring CPU diodes and inlet ambient conditions using a baseboard management controller (BMC) local to each system motherboard. These readings are then forwarded to a common control point (a Management Module) and chassis fan speeds are then adjusted accordingly. However, to implement this approach, each system board requires software customization to the local BMC and separate management module control hardware and software must be provided.